1. Field of the Invention
The present invention relates generally to suspension systems for automotive vehicles, and more particularly to stabilizers for improving lateral stability in suspension systems.
2. Scope of the Prior Art
Suspension systems for heavy-duty use in commercial vehicles typically employ air springs, and are used in single-axle units or in tandem arrangements of two or more axles. The axles can be either driven or non-driven.
An air spring is essentially an air-inflated bag and of itself has insignificant lateral stability. Therefore, in air spring suspensions it is necessary to provide mechanical means for controlling all lateral forces and force components on the suspension and its various members.
A typical suspension is shown in U.S. Pat. No. 3,140,880 to Masser in which air springs are disposed between two vertically swinging control arms to which the axle is also attached. One feature of that suspension is that much of the lateral force is controlled by a strong, relatively rigid attachment between the axle and the control arms.
It was found desirable to provide for greater flexibility of movement between the axle and the control arms, while still maintaining sufficient lateral stability. An improved suspension which has come into common use is shown in Masser U.S. Pat. No. 3,406,983 in which a transverse beam, connected to the control arms, transmits the spring load between the control arms and the vehicle frame. This beam provides a torsion member which resists differential vertical swinging movements of the control arms. One or more joints are provided in the beam or its connections to the control arms and these joints provide articulation, to a limited degree, of the control arms with respect to the beam. The joints incorporate elastomeric material which distort resiliently when the joints are twisted. This elastomeric material is dimensioned, configured and distributed so as to provide a generally predetermined resistance to each of the movements of the control arms with respect to the beams.
Attempts have been made to provide additional resistance to lateral forces which cause the frame to "roll" relative to the axle, without interfering with the vertical forces controlled by the springs themselves. Such rolling typically occurs, for example, by the centrifugal and acceleration forces acting on the frame when the vehicle turns. Prior art attempts to provide additional roll resistance include the addition of stabilizer bars, roll bars, or torsion bars secured between the suspension and the frame, or brackets extending between the axle and the frame. Additional roll resistance can also be provided by stiffening the flexible connection between the control arms and the beam.
Such improvements, however, may nevertheless affect the handling and ride of the vehicle, and transfer the load caused by the lateral forces to the frame. Such systems are frequently more complex, having many moving components and may also have limited application, especially where the vehicle center of gravity is higher than a predetermined level.